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    <title>Document</title>
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    <script>
        var arr = [1,2,3];
        console.log(arr.length);
        

        var len = arr.push(4,5,6,7);
        console.log(len);
        console.log(arr);

        /*
            push

            往数组的末尾添加一个或多个元素,返回当前被修改后的数组的最新长度
            该方法会改变原数组
        */
        
    </script>
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